The present invention relates to an improved process for the treatment of effluents and, in particular, to a biological process for the treatment of aqueous effluent wastes containing nitrogenous matter in the presence of carbonaceous matter.
Nitrogenous compounds, for example nitrate ions, nitrite ions, amines and/or ammonia are present in effluents obtained from many sources. Aqueous effluents from industrial sites, for example multi-product chemical plants, may contain carbonaceous and nitrogenous matter, e.g. nitric acid, ammonium nitrate, and the composition of these waste streams will depend on the source of the particular effluent. Effluents may contribute significantly to the pollution of lakes and streams, destruction of animal and plant life and may result in health hazards.
Chemical processes for the treatment of effluents are known. For example, a process for the treatment of effluent containing carbonaceous and nitrogenous matter in the presence of water at an elevated temperature is described in U.S. Patent Application Ser. no. 240,226, filed Mar. 31, 1972.
Biological processes for the treatment of aqueous effluents are also known. The conventional "activated sludge process" is an aerobic process in which an aqueous waste stream is contacted with activated sludge usually with accompanying aeration. Such a process may be adequate to remove carbonaceous matter from effluents but it may fail in the removal of nitrogenous matter, for example ammonia and nitrite ions, which it may only convert into a different form of nitrogenous matter, for example nitrate ions.
Biological processes are known for the denitrification of nitrogenous matter. For example, see "Nitrogen Removal by Nitrification and Denitrification", Walter K. Johnson and George J. Schroepfer, Water Pollution Control Federation Journal, Vol. 30 (August, 1964) No. 8, p. 1015-1036. An anaerobic process for the denitrification of nitrocellulose waste is described by K. Mudrack in "Nitro-Cellulose Industrial Waste", Purdue University Engineering Bulletin, Extension Service #121, 1966. Anaerobic denitrification processes are sensitive to the pH of the stream and it is preferred if the stream entering the denitrification process has been neutralized.
Another biological process for treating nitrates in aqueous streams is described by W. Haltrich in "Elimination of Nitrate from an Industrial Waste", Proceedings Purdue Industrial Waste Conference, May, 1967. In this process, the industrial waste containing the nitrate is mixed with activated sludge in an unaerated stage to split the nitrate followed by treatment in an aeration stage. In the article "Controlling Operation to Minimize Activated Sludge Effluent Nitrogen", Journal of Water Pollution Control Federation 34, 1962 pages 920-31, the authors L. J. Ludzack and M. B. Ettinger describe other biological processes for treating nitrogen-rich effluents.
In order to overcome injurious effects of phenols on bacteria under anaerobic conditions, Todhunter et al. in Canadian Patent No. 620,366 which issued May 16, 1961, disclosed and claimed a process in which phenols are treated aerobically prior to anaerobic treatment of ammonia.